1. Field of the Invention
The present invention relates to a cycloalkyl xcex2-glucoside, a xcex2-glucosidase inhibitor, an aromatic substance formation inhibitor that inhibits the formation of plant aromatic substance, and a plant or a part thereof in which the formation of aromatic substances is inhibited by the aforementioned aromatic substance formation inhibitor, as well as a plant life lengthening agent.
2. Description of Related Art
As inhibitors for enzymes which hydorolyzed glycosidic linkages such as glucosidase, various substances including saccharides and proteins derived from plants and microorganisms, synthetic oligosaccharide derivatives and the like have hitherto been reported. Among those, as for inhibitors of xcex2-glucosidase, many substances derived from microorganisms or plants and obtained by organic synthesis have been described. Examples of such substances include, as for those derived from microorganisms or plants, nojirimycin (T. Niwa et. al., Agric. Biol. Chem. 34. 966 (1970)), 1-deoxynojirimycin (G. Legler et. al., Carbohydr. Res., 128, 61 (1984)), castanospermine (U. Fuhrann et. al., Biochem. Biophys. Acta., 825, 95 (1985)), 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine (A. Welter et. al., Phytochem. 15, 747 (1976), validamine (S. Ogawa et. al., J. Chem. Soc. Chem. Commun., 1843 (1987) and the like, and as for those obtained by organic synthesis, aminocyclopentane polyol (R. A. Farr et. al., Tetrahedron Lett., 31, 7109 (1990), cyclic amidine (G. Papandreou et. al., J. Am. Chem. Soc. 115, 11682 (1993), cyclic guanidine (J. Lehmann et. al. Leiebigs Ann. Chem., 805 (1994), and the like. These inhibitors are analogues of the substrates for glucosidases containing a nitrogen atom without exception.
These inhibitors are useful physiological active substances which can be used for various biochemical researches as an enzyme reaction analysis reagent, an affinity carrier, a agent for analysis of function and recognition mechanism of glycoprotein and the like, and it has also been attempted to utilize them as medical or agricultural chemicals in these days. These inhibitors which are expected to be applicable in various fields, as mentioned above, have been conventionally been produced by extraction from microorganisms or plants, or by organic synthesis.
However, in the case of those substances derived from microorganisms, it is quite difficult to purify such inhibitors from microbial culture broth. As for those ones derived from plants, their present amount is very little in the first place, and hence it is difficult to extract and purify them from plants. Thus, the both methods involve many problems as a method for industrial production. For example, they suffer from limitations concerning with cost, yield and the like. Further, most of reported conventional xcex2-glucosidase inhibitors are their substrate analogues containing a nitrogen and therefore it is not easy to produce them through enzymatic synthesis or organic synthesis. That is, in the case of organic synthesis, only for introducing a nitrogen atom into a saccharide structure, several steps of organic synthesis reaction are required to perform, and hence it is disadvantageous as an industrial process. For the aforementioned reasons, it has hitherto been difficult to industrially produce glucosidase inhibitors which is utilizable for biochemical applications. Therefore, there has been desired an inhibitor having a relatively simple structure of which industrial production is possible.
By the way, a method for changing plant fragrance has been known, which comprises allowing a plant to absorb an aromatic substance, xcex2-glucoside (Japanese Patent Unexamined Publication [KOKAI] No. 6-336401). This method consists, of adding aroma to a plant. Therefore, it was insufficient for improving aroma of plant with an unpleasant smell. Further, there has also been known changing plant fragrance by adding a dihydric alcohol such as propylene glycol as plant fragrance deodorizing agent (Japanese Patent Unexamined Publication [KOKAI] No. 10-33647). Although this patent document describes that unpleasant smell of plant could be deodorized by adding a dihydric alcohol, its effectiveness was not satisfactory one. Further, while it is of course required to reduce fragrance of plants generally considered to be unpleasant, for example, that of gypsophila, lily, chrysanthemum etc., it may be also desirable as the case may be to reduce fragrance of plants considered pleasant, for example, that of rose, jasmine, lavender and the like. Therefore, it has been desired to develop an aromatic substance formation inhibitor that acts on any kind of aroma.
Currently, as plant aromatic substances, there are known, for example, monoterpene alcohols such as geraniol and citronel, aromatic alcohols such as phenethyl alcohol and benzyl alcohol and the like. These alcohols are contained in various flowers, teas, fruits, wines and the like, and it has become clear that they also exist as glycosides in addition to their free forms. Further, there have also been reported that the aromatic substance precursors of the aromatic substances such as geraniol and phenethyl alcohol, which are major aromatic substances of rose and the like, are xcex2-glucosides, and biosynthesized in leaves and petals, respectively, and that xcex2-glucosidases play an important role in the production process of aromatic substances (I. E. Ackermann et. al., J. Plant Physiol., 134, 567-572 (1989); K. Sakata, Oyo Tositsu Kagaku [Applied Saccharide Science], Vol.45, No.2, 123-129 (1998)).
That is, plant fragrance is formed by a mechanism that the aromatic substance precursor, xcex2-glucoside, is hydrolyzed by xcex2-glucosidase to liberate an aromatic substance. If the function of xcex2-glucosidase in this mechanism can be inhibited, the aromatic substance precursor, xcex2-glucoside, would not be hydrolyaed, and hence an aromatic substance will not be formed or its formation will be reduced. That is, it can be considered that, if xcex2-glucosidase can be inhibited, the aromatic substance to be liberated is reduced and smell can be reduced.
Therefore, an object of the present invention is to provide a novel compound that has xcex2-glucosidase inhibition activity and can easily be produced in an industrial process. Furthermore, another object of the present invention is to provide an aromatic substance formation inhibitor containing such a novel compound as an active ingredient, and plant or part thereof in which the formation of aromatic substances is inhibited by the aforementioned aromatic substance formation inhibitor.
As a result of the present inventors"" researches, it was found that cycloalkyl xcex2-glucosides which can be easily produced by organic synthesis or enzymatic synthesis had the xcex2-glucosidase inhibition activity. Because these xcex2-glucosides do not contain a nitrogen atom, their synthesis does not require any complicated synthetic process for introducing a nitrogen atom, and hence they can be produced by a relatively simple synthetic process, which means that their industrial production is possible. Furthermore, the present inventors studied various candidate aromatic substance formation inhibitors for plants from the viewpoint of searching substances capable of inhibiting xcex2-glucosidase to prevent the hydrolysis of xcex2-glucoside, thereby inhibiting the formation of aromatic substances, to find aromatic substance formation inhibitors for plants that have suitable activity for alleviating unpleasant smell and strong aroma of plants. As a result, it was unexpectedly found that the aforementioned cycloalkyl xcex2-glucosides had marked activity for inhibiting the formation of plant aromatic substances and consequently reducing the amount of aromatic substances released from plants, and further found that they did not producing phytotoxicity against plants and also had life lengthening effect. Thus, they accomplished the present invention.
The present invention relates to compounds represented by the following general formula (I). 
In the formula, R represents a cyclic hydrocarbon group, and n represents 0 (zero) or an integer not less than 1.
The present invention also relates to a xcex2-glucosidase inhibitor which contains at least one of compound represented by the aforementioned general formula I as an active ingredient; an aromatic substance formation inhibitor which contains at least one of compound represented by the aforementioned general formula I as an active ingredient; a plant or a part thereof in which formation of aromatic substance is inhibited by the aforementioned aromatic substance formation inhibitor; and a plant life lengthening agent which contains at least one of compound represented by the aforementioned general formula I as an active ingredient.
In the general formula (I), n is 0 (zero) or an integer not less than 1, and does not have any particular upper limit. However, considering ease of production, for example, if a raw material is commercially available or not, n is preferably 3 or less. Of course, it is not intended to exclude those compounds where n is 4 or more.
In the general formula (I), R represents a cyclic hydrocarbon group, and specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and the like. Specifically, it can be selected from the group consisting of a cyclopropylmethyl group, a cyclopentylmethyl group, a 2-cyclopentylethyl group, a 3-cyclopentylpropyl group, a cyclobutyl group, a cyclopentyl group and the like. Examples of the compound of the present invention represented by the aforementioned general formula (I) are, specifically, cyclopropylmethyl xcex2-glucoside, cyclobutyl xcex2-glucoside, cyclobutylmethyl xcex2-glucoside, cyclopentyl xcex2-glucoside, cyclopentylmethyl xcex2-glucoside, 2-cyclopentylethyl xcex2-glucoside, 3-cyclopentyl-1-propyl xcex2-glucoside and the like.
The cycloalkyl xcex2-glucoside of the present invention can be synthesized either by an organic synthetic process or enzymatic synthesis process. For the organic synthesis process, a method comprising a known reaction of glucose and alcohol in the presence of an acid catalyst can be used, and the compounds can be readily produced by one step through such a method (see Japanese Patent Unexamined Publication [KOKAI] No. 48-32846). As the aforementioned catalyst, hydrochloric acid, sulfuric acid, strongly acidic cation exchange resin and the like can be used. The cycloalkyl xcex2-glucoside can be produced by adding the catalyst to a mixture of saccharide and alcohol, and stirring the mixture at a reaction temperature of 0-100xc2x0 C. In addition to the above method, a method utilizing the known Koenigs-Knorr reaction to exclusively synthesize a xcex2-linked compound (Yu Kagaku [Oil Science], Vol. 43, No. 1, 31-38, (1994)) can also be used for the present invention.
As for the enzymatic synthesis process, the compound can readily be synthesized by utilizing the known transglucosylation reaction by xcex2-glucosidase (see Japanese Patent Unexamined Publication No. 63-25859). Specifically, the xcex2-glucoside can be produced by utilizing a cellulosic saccharide such as cellobiose, holocellulose, and xylan as a donor substrate, and an alcohol as an acceptor substrate, and allowing xcex2-glucosidase to act on them.
As the cyclic alcohol used as a raw material in the aforementioned organic synthesis or the enzymatic synthesis, cyclopropanol, cyclobutanol, cyclobutylmethanol, cyclopentanol, cyclopentylmethanol, 2-cyclopropylethanol, 3-cyclopropyl-1-propanol and the like can be mentioned.
The obtained product containing xcex2-glucoside can be further purified if required. As the method which can be used for the purification, for example, gel filtration chromatography, strongly acidic cation exchange resin chromatography, adsorption chromatography and the like can be mentioned. Specifically, the purification can be performed as follows. A reaction mixture of organic synthesis or enzymatic reaction is loaded on a column filled with a synthetic adsorption resin so that the cycloalkyl xcex2-glucoside should be adsorbed on the resin, and the column is washed with water for removing un-adsorped materials. Then, the adsorbed cycloalkyl xcex2-glucoside is eluted with 30 to 100% methanol to obtain concentrated cycloalkyl xcex2-glucoside. The obtained concentrate can further be purified by gel filtration chromatography.
The xcex2-glucosidase inhibitor of the present invention comprises as an active ingredient at least one of the xcex2-glucoside represented by the aforementioned general formula (I). The xcex2-glucoside represented by the aforementioned general formula (I) and the group R and the cyclic hydrocarbon group in the general formula (I) are similar to those explained above for the cycloalkyl xcex2-glucoside of the present invention.
While the xcex2-glucosidase inhibitor of the present invention can be used for both of xcex2-glucosidases derived from plant and microorganism, it can preferably be used for xcex2glucosidase derived from plant.
The aromatic substance formation inhibitor of the present invention comprises as an active ingredient at least one of the xcex2-glucoside represented by the aforementioned general formula (I). The xcex2-glucoside represented by the aforementioned general formula (I), and the group R and the cyclic hydrocarbon group in the general formula (I) are similar to those explained above for the cycloalkyl xcex2-glucoside of the present invention.
The aromatic substance formation inhibitor of the present invention can be used for the inhibition of plant aromatic substance formation. As the plant of the present invention, therophytes, perennial herbaceous plants, and flowering trees such as gypsophila, lily, chrysanthemum, rose, jasmine, lavender, tulip, carnation, orchid, and sweet pea can be mentioned. However, it is not limited to these categories. The aromatic substance formation inhibitor of the present invention inhibits the formation of aromatic substance by inhibiting the aromatic substance formation in plant bodies. Therefore, the plant of which formation of the aromatic substance should be inhibited may be one in a state that the aromatic substance can be formed. For example, they may be cut flowers or those cultured in open, house, flowerpot and the like.
Since the aromatic substance formation inhibitor of the present invention exhibits high solubility in water and storage stability as an aqueous solution, it can be used as an aqueous solution, for example. Since the aromatic substance formation inhibitor of the present invention inhibits the activity of xcex2-glucosidase in a plant body, the inhibitor must be introduced into the plant body in order to obtain the aromatic substance formation inhibition effect in the plant body by the inhibitor. To this end, for example, the following methods can be used.
When an aqueous solution is used for inhibiting the formation of the aromatic substance of plants, for example, in the case of cut flowers, cut ends of the cut flowers can be immersed in the aqueous solution of the aromatic substance formation inhibitor of the present invention, and thereby the aromatic substance formation inhibitor of the present invention can be absorbed through vessels of the cut flowers. This operation can be carried out easily, since special treatment is not required. Furthermore, such an aqueous solution as mentioned above can similarly be used in many scenes, for example, when flowers are temporarily immersed in water after the harvest by producers, when cut flowers are sold in shops such as flower shops in containers such as buckets, when cut flowers are arranged in vases at home, hospital, exhibition, etc. and the like. Further, such an aqueous solution can also be used for affusion or direct spraying on leaf surfaces so that the inhibitor should be absorbed in a plant, thereby inhibiting the formation of the aromatic substance of the plant. This method can be used for, for example, cut flowers and plants grown on open, in houses, flowerpots and the like. Specifically, an aqueous solution of the aromatic substance formation inhibitor of the present invention in a suitable amount can be affused into soil or sprinkled on leaf surfaces of plants.
Although concentration of the cycloalkyl xcex2-glucoside used as an aromatic substance formation inhibitor of the present invention may vary depending on the kind of objective cut flowers or treatment time, when used as an aqueous solution, it is generally preferable to use it within a concentration range of about 0.01 to 10% by weight volum, more preferably about 0.1 to 3.0% by weight volum. The aromatic substance formation inhibitor of the present invention can function so long as the cycloalkyl xcex2-glucoside functions as an active ingredient. Therefore, the aromatic substance formation inhibitor and plant or a part thereof of which formation of aromatic substance is to be inhibited may contain impurities, specifically, impurities introduced during the organic synthesis or enzymatic synthesis, so long as the plant is not adversely affected.
Furthermore, the aromatic substance formation inhibitor of the present invention can be used with a known cut flower life lengthening agent, for example, those comprising saccharide and germicide, surface active agent and the like, if required. Furthermore, the aromatic substance formation inhibitor of the present invention can also contain conventionally used nutrients such as nitrogen source, phosphoric acid, potassium source, sucrose, glucose, and vitamin C, trace amount nutrients such as iron, zinc, manganese, copper, and boron, B-nine, benzyladenine, brassinolide and the like.
The plant or part thereof in which the formation of the aromatic substance is inhibited by the aromatic substance formation inhibitor of the present invention means a plant or a part thereof in which the formation of the aromatic substance is inhibited by the aforementioned method utilizing the aromatic substance formation inhibitor of the present invention. The plant may be, for example, cut flowers or those cultured in open, house, flowerpot and the like. The part of plant may be, for example, a flower or a part containing flower, leaf or a part containing leaf, stalk or a part containing stalk and the like. As the kind of the aforementioned plant, for example, therophytes, perennial herbaceous plants, and flowering trees such as gypsophila, lily, chrysanthemum, rose, jasmine, lavender, tulip, carnation, orchid, and sweet pea can be mentioned. However, it is not limited to these categories.
Since formation of unpleasant aroma or aroma desired to be reduced is prevented in the plant or part thereof of the present invention, the emitted aromatic substance therefrom is reduced compared with that originally emitted from the corresponding plant or part thereof. Therefore, the plant or part thereof can be used for their applications without caring about their aroma. Specifically, when the aromatic substance formation of lily cut flowers is inhibited, they can be used for indoor decoration or the like without caring about their aroma, since their aroma said to be unpleasant is reduced.
The plant life lengthening agent of the present invention comprises as an active ingredient at least one of the xcex2-glucoside represented by the aforementioned general formula (I). The xcex2-glucoside represented by the aforementioned general formula (I), and the group R and the cyclic hydrocarbon group in the general formula (I) are similar to those explained above for the cycloalkyl xcex2-glucoside of the present invention.
While the action mechanism of the plant life lengthening agent of the present invention is not clear, it gives to plant bodies life lengthening effect without causing phytotoxicity. As the plant of the present invention, therophytes, perennial herbaceous plants, and flowering trees such as gypsophila, lily, chrysanthemum, rose, jasmine, lavender, tulip, carnation, orchid, and sweet pea can be mentioned. However, it is not limited to these categories. The plant life lengthening agent of the present invention can be used for cut parts of the aforementioned plants, for example, cut flowers.
Since the plant life lengthening agent of the present invention is excellent in solubility in water and storage stability as an aqueous solution, it can be used as an aqueous solution, for example. When an aqueous solution is used for lengthening plant life, methods and amounts similar to those used for the aqueous solution of the aromatic substance formation inhibitor of the present invention for cut flowers can be used.